Drying module

ABSTRACT

A dryer module for drying filter supports in DNA preparation comprises a receiving member for receiving the filter support and at least one blower member, the blower member being arranged below the receiving member for receiving the filter support so that the filter support is blown on an dried from below. The dryer module also has a heating system for warming the air blown from below against the filter support, the heating system being arranged above the blower member, of which there is at least one. The dryer module is electronically controlled by a control means as a function of the measured temperature of the drying air. The dryer module can be used as a stand-along apparatus or in an automated environment.

The invention relates to a dryer module for drying filter supports, asused in DNA preparation.

In modern DNA preparation procedures, the products of which are to beused in sequencing tasks, it is becoming clear, especially in the caseof the more recent megasequencing projects (Human Genome Project), thatautomation of the labour-intensive manual steps is indispensable.Whereas previously so-called “ready-to-use kits” that simplified theworking up of DNA sequences introduced by cloning were not available,today there are already a few commercially available aids in existencethat are also suitable for automatically working through thecorresponding protocols (such as, for example, the widespread Qiagenprotocol) using robots.

The preparation protocol described by Qiagen comprises washing withethanol-containing buffer the DNA adsorbed on filter elements of afilter support. Experiments have shown that traces of ethanol have aseverely adverse effect on the result of the subsequent sequencingreactions. The participating enzymes are probably inhibited by ethanol.In this step, initially the larger amounts of ethanol are removed fromthe filters in known manner. When the protocol is carried out, forexample, in an appropriate vacuum apparatus, the removal can be achievedby the vacuum being applied for longer than would be necessary for thepurpose of removing the washing liquid. The air flow generated in thefilter in that manner removes the larger amounts of ethanol from thefilters, but the particular construction of the Qiagen filter supportscauses contamination of the subsequent sequencing process if no specialprecautions are taken, since residues of ethanol remain on the wallsbetween the outlet nozzles and the plastics housings on the underside ofthe filter support. Contamination by ethanol was also observed duringthe elution of the DNA from the filter material, the contaminationoccurring as follows: as the eluate is being sucked off into the eluatecollectors, a drop forms on the outlet nozzle. Before that drop is drawnoff it “migrates” upwards on the nozzles and comes into contact with theethanol-containing liquid still to be found there. Mixing consequentlyoccurs. The drop is then drawn off and falls into the eluate collector.The result is a general contamination of the eluate with ethanol to suchan extent that the sequencing batch is “poisoned”.

The problem underlying the invention is therefore to provide anapparatus by which the remaining residual alcohol is removed from filtersupports, as used, for example, in the Qiagen protocol.

This problem is solved by the features of claim 1. The subsidiary claimsrelate to advantageous configurations of the invention.

The invention relates to a dryer module for drying filter supports inDNA preparation, wherein the dryer module has a receiving member forreceiving the filter support, and at least one blower member, the blowermember being arranged below the receiving member for receiving thefilter support so that the filter support is blown on and dried frombelow.

Preferably, the dryer module according to the invention has at least oneheating element for warming the air blown from below against the filtersupport.

Furthermore, an air shaft for guiding the drying air is arranged betweenthe blower and the receiving member for the filter support, in which airshaft the heating elements are arranged.

Advantageously, the blower member is formed by a crossflow blower whichis driven by an electric motor.

Furthermore, the upper end of the air shaft can be formed as a nozzlefor channeling the lateral air flow.

Advantageously, the receiving member for the filter support is formed asa centring plate, the centring plate being arranged on foot members sothat the centring plate, together with the foot members, forms a filtersupport stand.

Also, the dryer module can be arranged in an opening in a bench top. Thedryer module can, however, also be operated as an individual piece ofapparatus, either in an automated environment or as a stand-aloneapparatus.

Advantageously, the step of removing the ethanol from the region betweenthe outlet nozzle and the plastics housing of the filter support is notcarried out manually but is automated. For that purpose, the dryermodule blows warmed air (50° C. maximum) from below against the filtersupport and evaporates the ethanol. The filter dried in that way isintroduced into a vacuum chamber again in order to be aerated once morefor a certain time by the application of a vacuum. In that second step,remaining traces of ethanol are further removed. Finally, the filtertreated in that way is again placed on the dryer module so as to ensure,by means of the heated air flow, that any possible traces of ethanolstill present are finally evaporated off. Only then is the filtersupport, for example, reinserted into the pipetting robot in order forthe eluant to be pipetted in for the purpose of releasing the DNA fromthe filters.

A preferred embodiment of the invention is described in the followingwith reference to the drawings in which

FIG. 1 is a diagrammatic cross-section through a dryer module fixed in abench top,

FIG. 2 is a cross-section of the dryer module rotated through 90°relative to the view in FIG. 1,

FIG. 3 is a view of the dryer module according to the invention frombelow, and

FIG. 4 is a cross-section of a filter support employed.

In the preferred embodiment shown in FIG. 1, two crossflow blowers 1 arecoupled along their longitudinal sides in order to achieve an air flowthat is as far as possible homogeneous. A uniform air flow is thusgenerated over the entire face of the filter support (not showing) to bedried. The outlet surface area of the air shaft 4, which in thepreferred embodiment is 8 cm×12.5 cm, is somewhat larger than the basesurface area of the filter support to be dried. The air flow is 2×80m³/h maximum and can be regulated, by means of a transformer (not shown)connected upstream, by way of the rotational speed of the motors 3 ofthe pair of crossflow blowers 1.

The rectangular air shaft 4 is so constructed that the air flow ischanneled identically to a nozzle 6 toward the outlet opening. It ismade of 2 mm-thick sheet iron and soldered together to form a closedshape. Arranged in the lower region thereof is a receiver for a heatingsystem 5, below which the two crossflow blowers 1 are secured. The upperportion of the air shaft 4 is fastened in a correspondingly dimensionedopening in a bench top 7 and thus fixed at a precisely defined positionin the work area. The heating elements 5 a, 5 b and the blower members 1are as a result of this arrangement located below the workbench 7. Theopening of the air shaft 4 is preferably at the same level as theworking surface of a robot bench (not shown) in cases where the dryermodule is used in an automated process.

In the preferred embodiment, the heating system 5 consists of twoheating elements 5 a, 5 b, as will become clearer in FIGS. 2 and 3. Theheating elements 5 a, 5 b are fixed across the outlet opening of thecrossflow blowers 1. In each case two mica multi-perforated plates areused as supports for a heating wire, which is mounted in the air flow inthe form of coils spaced approximately 3 mm apart and thus heats the airflow uniformly. The coils are so created that the reverse loop comes tolie outside the air flow, while the heating wires, which extend inparallel, are arranged at right angles to the mica multi-perforatedplates.

The filter stand, consisting of a receiving member 11 and supportingmembers 10, is so designed that it has centring members (shown in FIG.3) at its contact points with the filter support (not shown). 30° bevelsin the regions where the spacer sleeves (see FIG. 4) come into contactwith a filter support are to be given special mention. In the preferredembodiment, the filter stand comprises an upper supporting plate orcentring plate 10 acting as a receiving member, which has centringmembers, that is to say recesses for the spacer sleeves and the bearingface for the edge of the filter support. Fixed to that centring plate atthe four corner points are 4.5 cm-high supporting members 10, the lowerends of which each have a fastening bolt 8 measuring 0.3 cm. Those bolts9 fix the filter support stand exactly above the air outlet shaft 4 ofthe dryer module by engaging in corresponding bores in a plate 8, whichis arranged on the workbench, in order to fasten the stand. In thepreferred embodiment, the plate 8 is made of acrylic material. Once thefilter support, which is illustrated in FIG. 4, has been inserted, theoutlet nozzles thereof are located approximately 3 cm above the upperedge of the air shaft 4.

The control of the blower members 1 and the control of the heatingelements 5 a, 5 b are carried out separately by a controller interface.It is thus possible for the heating system 5 to be switched off firstafter the drying operation is complete, so that the blowing, which isthen having a cooling effect on the heating wires, is terminated after atime delay. In order for the temperature to be measured, a lateralrecess 13 is provided in the nozzle 6 for receiving a temperaturesensor. The heating elements 5 a, 5 b are controlled by a temperaturethreshold circuit.

FIG. 2 is also a cross-section of the dryer module according to theinvention, but the cross-section is rotated through 90° about thevertical axis of symmetry in relation to the view in FIG. 1. It ispossible to see the two parallel crossflow blower barrels 1, which aredriven by corresponding motors 3. The two heating elements 5 a, 5 b ofthe heating system 5 are arranged in parallel and virtually abutting oneanother in the air shaft 4. Above the heating elements, the nozzle 6 isformed as a component of the shaft 4 for the purpose of channeling thedrying air. In the embodiment shown here, the dryer module is fastenedin the opening of a bench top 7 or similar. Arranged on the bench top 7is a plate 8, preferably made of acrylic material or a similar material,which carries the filter support stand consisting of the supportingmembers 9 and the centring plate 11, the filter support stand beingfixed and aligned in the plate 8 by means of fastening bolts 9.

FIG. 3 shows the above-described dryer module from above. Referring toFIG. 3, it should be taken into account that, in the preferredembodiment, the plate 8 consists of acrylic material and is thereforetransparent. Illustrated are two crossflow blowers 1 with driveconnections 2 and motors 3, and the heating elements 5 a and 5 b in theair shaft 4, which forms a nozzle 6. The centring plate 11 has fourcentring shafts 12 for receiving correspondingly shaped spacer sleevesof the filter support, which sleeves are shown in FIG. 4. The centringshafts 12 enforce the alignment of the filter support.

For the purpose of illustration, FIG. 4 shows a cross-section through afilter support 14 as normally used, which is formed by a plurality offilter elements 15 connected to one another in known manner. Usually,the filter support is of rectangular shape in plan view. The outerfilter elements 15 of the filter support 14 have spacer sleeves 17,which are used to centre the filter support 14 in an automatedenvironment. In the case illustrated, they are used for the purpose ofcentring in the centring shafts 12 of the centring plate 11. The filtersupport 14 also has a circumferential wall 18 in the shape of a crown.When the filter support is being inserted into the centring plate 11 ofthe dryer module, first of all the spacer sleeves 17 engage in thecentring shafts 12, and the filter support 14 is moved downwards, forexample by a robot, until the wall 18 sits on the centring plate 11 andthe filter support 14 thus adopts its final position. The dryer moduleis then ready for operation.

List of Reference Numerals 1 crossflow blower barrels 2 drive connection3 motor 4 air shaft 5 heating system 5a, 5b heating element 6 nozzle 7bench top 8 acrylic plate 9 fastening bolts 10 stand 11 centring plate12 centring shaft 13 temperature sensor receiver 14 filter support 15filter element 16 filter element nozzle 17 spacer sleeve 18 wall

What is claimed is:
 1. Dryer module for drying a filter support (14) inthe context of DNA preparation, having a heating system (5) and a blowermember (1), the heating system (5) being arranged downstream of theblower member (1) and a filter (15) arranged in a filter support (14)being blown on and dried from below, wherein the filters (15) arearranged suspended in the filter support (14) and the filter support hasspacer sleeves (17) that are insertable into corresponding centringshafts (12) in a centring plate (11) for receiving the filter support(14), the heating system (5) comprising heating wires, which extend inparallel over a rectangular cross-section of an air shaft (4) and whichare arranged at right angles to the air flow and upstream of thecentring plate (11), and the dryer module having a crossflow blower asblower member (1).
 2. Dryer module according to claim 1, wherein theblower member (1) is driven by an electric motor (3).
 3. Dryer moduleaccording to claim 1, wherein a nozzle (6) for channeling the air flowis arranged between the air shaft (4) and the centring member (11) forthe filter support (14).
 4. Dryer module according to claim 1, whereinthe dryer module is arranged in an opening in a bench top (7).
 5. Dryermodule according to claim 1, wherein the centring plate (11) forreceiving the filter support is arranged on supporting members (10). 6.Dryer module according to claim 2, wherein the module has a temperaturesensor.
 7. Dryer module according to claim 6, wherein the module has anelectrical control means for controlling the motor (3), of which thereis at least one, and the heating system (5), the heating system beingcontrolled as a function of the temperature measured by the temperaturesensor.
 8. Dryer module according to claim 7, wherein the control meansis provided with a delay circuit which, when the dryer module isswitched off, causes the blower member (1), of which there is at leastone, to be switched off chronologically after the heating system (5) isswitched off.
 9. Use of the dryer module according to claim 1 in anautomated environment.
 10. Use of the dryer module according to claim 1as a stand-alone apparatus.